Catapres General Information

An alpha-2 adrenergic agonist that crosses the blood-brain barrier. Catapres acts centrally by reducing sympathetic tone, resulting in a fall in diastolic and systolic blood pressure and a reduction in heart rate. It also acts peripherally, and this peripheral activity may be responsible for the transient increase in blood pressure seen during rapid intravenous administration. (From Martindale, the Extra Pharmacopoeia, 30th ed, p350)

Catapres - Pharmacology:

Catapres acts as an agonist at presynaptic alpha(2)-receptors in the nucleus tractus solitarius of the medulla oblongata. Stimulation of these receptors results in the supression of efferent sympathetic pathways and the subsequent decrease in blood pressure and vascular tone in the heart, kidneys, and peripheral vasculature. Catapres is also a partial agonist at presynaptic alpha(2)-adrenergic receptors of peripheral nerves in vascular smooth muscle.

Catapres for patients

Tablet

Patients who engage in potentially hazardous activities, such as operating machinery or driving, should be advised
of a potential sedative effect of clonidine. Patients should be cautioned against interruption of clonidine
hydrochloride therapy without a physicians advice.

Epidural Injection

Patients should be instructed about the risks of rebound hypertension and warned not to discontinue clonidine
except under the supervision of a physician. Patients should notify their physician immediately if clonidine
administration is inadvertently interrupted for any reason. Patients who engage in potentially hazardous activities,
such as operating machinery or driving, should be advised of the potential sedative and hypotensive effects of
epidural clonidine. They should also be informed that sedative effects may be increased by CNS-depressing drugs such
as alcohol and barbiturates, and that hypotensive effects may be increased by opiates.

Catapres Interactions

Tablet

If a patient receiving clonidine hydrochloride is also taking tricyclic antidepressants, the effect of clonidine
may be reduced, thus necessitating an increase in dosage. Catapres hydrochloride may enhance the CNS-depressive
effects of alcohol, barbiturates or other sedatives. Amitriptyline in combination with clonidine enhances the
manifestation of corneal lesions in rats

Epidural Injection

Catapres may potentiate the CNS-depressive effect of alcohol, barbiturates or other sedating drugs. Narcotic
analgesics may potentiate the hypotensive effects of clonidine. Tricyclic antidepressants may antagonize the
hypotensive effects of clonidine. The effects of tricyclic antidepressants on clonidines analgesic actions are not
known.

Beta blockers may exacerbate the hypertensive response seen with clonidine withdrawl. Also, due to the potential
for additive effects such as bradycardia and AV block, caution is warranted in patients receiving clonidine with
agents known to affect sinus node function or AV nodal conduction (e.g., digitalis, calcium channel blockers,
and beta-blockers.)

There is one reported case of a patient with acute delirium associated with the simultaneous use of fluphenazine
and oral clonidine. Symptoms resolved when clonidine was withdrawn and recurred when the patient was rechallenged
with clonidine.

Epidural clonidine may prolong the duration of pharmacologic effects of epidural local anesthetics, including both
sensory and motor blockade.

Catapres Contraindications

Tablet

None known.

Epidural Injection

Catapres HCl is contraindicated in patients with a history of sensitization or allergic reactions to clonidine.
Epidural administration is contraindicated in the presence of an injection site infection, in patients on
anticoagulant therapy, and in those with a bleeding diathesis. Administration of epidural clonidine HCl above the C4
dermatome is contraindicated since there are no adequate data to support such use